Arc-resistant switchgear enclosures house medium voltage electrical switchgear components such as potential transformers (PT), fuses, circuit breakers, etc. A typical enclosure has plural compartments, with each compartment housing one or more electrical components. Medium voltage generally is in the 5-38 KVA range.
During normal operation, the switchgear components generate heat and require air circulation for cooling. The enclosure has vents to provide cooling. For example, an intake or inlet vent may be on or near a front access door. Air is drawn in through the inlet vent, is heated by the switchgear components, rises and exits through vents in the top of the enclosure, into a plenum.
However, such medium voltage electrical components can experience arc faults. An arc fault creates an explosion of hot gasses which can endanger nearby personnel and equipment.
In order to protect nearby personnel and equipment, enclosures are metal clad and are designed to contain the explosion and vent the explosive gasses in a controlled manner. Personnel and equipment at the front, sides and rear of an enclosure are protected by the walls of the enclosure. The explosive gasses are typically vented up into a plenum which channels the explosive gasses to a safe area, such as a building exterior.
When an arc fault explosion initiates, the intake vents, which are typically on or below the doors, must be closed to prevent the escape of hot gasses. Thus, the challenge lies in designing a vent that is open during normal operation to allow for ventilation and cooling of the enclosure components, but which suddenly closes, and remains closed, during an arc fault explosion in the compartment.